Tubular phosphate transport: a comparison between different methods of urine sample collection in FGF23-dependent hypophosphatemic syndromes

OBJECTIVES

Tubular maximum phosphate reabsorption per glomerular filtration rate (TmP/GFR) is used to evaluate renal phosphate reabsorption and it is a useful tool for the differential diagnosis of hypophosphatemic syndromes. TmP/GFR is typically calculated from fasting plasma and second morning void urine samples, obtained 2 h after the first void (TmP/GFR 2 h). The purpose of this study was to evaluate if TmP/GFR calculated from 24 h urine collection (TmP/GFR 24 h) can be used as an alternative for TmP/GFR 2 h in patients with urine phosphate wasting.

METHODS

We enrolled adult patients with X-linked hypophosphatemia (XLH) or tumor-induced osteomalacia (TIO). All patients underwent blood and urine sample collections, to calculate TmP/GFR 24 h and TmP/GFR 2 h.

RESULTS

Twenty patients (17 XLH and 3 TIO), aged 24-78 years, were included. All patients had low TmP/GFR 2 h (0.35 mmol/L, IQR 0.24-0.47 mmol/L) and TmP/GFR 24 h (0.31 mmol/L, IQR 0.22-0.43 mmol/L). The concordance correlation coefficient between TmP/GFR 2 h and TmP/GFR 24 h was 0.86 (95 % CI: 0.69-0.93), with a systematic bias of 0.05 mmol/L (95 % limits of agreement: -0.10 to 0.20). Furthermore, in 70 % (i.e., 14 patients out of 20) and 80 % (i.e., 16 patients out of 20) of cases the difference between TmP/GFR 2 h and TmP/GFR 24 h was within ±30 % and ±35 %, respectively.

CONCLUSIONS

Despite TmP/GFR 2 and 24 h show a relatively suboptimal agreement, the difference between the two parameters appears to be small and not clinically significant in the setting of adult patients with FGF23-dependent urine phosphate wasting and secondary hypophosphatemia.

[High-intensity interval training (HIIT) induces hepatic ketone body production possibly through altering expression of mTORC1, PPARα and FGF21 in mice]

The present study aims to investigate the production of ketone body in the liver of mice after 6 weeks of high-intensity interval training (HIIT) intervention and explore the possible mechanisms. Male C57BL/6J mice (7-week-old) were randomly divided into control and HIIT groups. The control group did not engage in exercise, while the HIIT group underwent a 6-week HIIT (10° slope treadmill exercise). Changes in weight and body composition were recorded, and blood ketone body levels were measured before, immediately after, and 1 h after each HIIT exercise. After 6-week HIIT, the levels of free fatty acids in the liver and serum were detected using reagent kits, and expression levels of regulatory factors and key enzymes of ketone body production in the mouse liver were detected by Western blot and qPCR. The results showed that, the blood ketone body levels in the HIIT group significantly increased immediately after a single HIIT and 1 h after HIIT, compared with that before HIIT. The body weight of the control group gradually increased within 6 weeks, while the HIIT group mice did not show significant weight gain. After 6-week HIIT, compared with the control group, the HIIT group showed decreased body fat ratio, increased lean body weight ratio, and increased free fatty acid levels in liver and serum. Liver carnitine palmitoyl transferase-I (CPT-I), peroxisome proliferator activated receptor α (PPARα), and fibroblast growth factor 21 (FGF21) protein expression levels were up-regulated, whereas mammalian target of rapamycin complex 1 (mTORC1) protein expression level was significantly down-regulated in the HIIT group, compared with those in the control group. These results suggest that HIIT induces hepatic ketone body production through altering mTORC1, PPARα and FGF21 expression in mice.

The rationale for intermittent administration of PTH in the management of mineral and bone disorder of chronic kidney disease

A major complication of chronic kidney disease is the derangement of mineral metabolism, leading to increased risk of fractures and cardiovascular mortality. Current therapeutic regimens are focused on reducing parathyroid hormone levels caused by secondary hyperparathyroidism, and the active vitamin D metabolite l,25(OH)2D, with limited success. It may be a more effective approach, however, if we could target the delayed response of parathyroid hormone in the early retention of phosphate following loss of renal function.We propose intermittent administration (even in stage 2 chronic kidney disease) of parathyroid hormone, known for its bone anabolic effects compared to the catabolic effects of the continuously elevated parathyroid hormone associated with the hyperparathyroid state, to mitigate the retention of phosphate. This approach may prevent the compensatory responses of the other two major calcium- and phosphate-regulating hormones (FGF-23 and l,25(OH)2D) that lead to further worsening of the derangement of mineral metabolism.In addition to its strong theoretical basis, there are data supporting the need for further research focused on the use of intermittent parathyroid hormone in the management of chronic kidney disease-mineral bone disorder.

QTc Interval Prolongation Is Independently Associated with FGF23 and Predicts Mortality in Predialysis Chronic Kidney Disease

INTRODUCTION

QTc interval prolongation is increasingly frequent as chronic kidney disease (CKD) advances and predicts death in dialysis. However, predictors and mortality risk in predialysis CKD are understudied. FGF23 induces left ventricular hypertrophy (LVH) which is associated with QTc interval prolongation and death, suggesting a possible pathway from FGF23 to death that entails LVH and QTc prolongation. We looked for links between FGF23 and prolonged QTc intervals mediated by LVH and for deaths associated with QTc prolongation in a prospective observational cohort of patients with predialysis CKD.

METHODS

Participants underwent protocolized baseline and semiannual FGF23 testing, baseline and study end echocardiograms, and baseline and annual electrocardiograms over 3 years.

RESULTS

A total of 2,254 participants (34.1% female; mean age: 68.7 years; mean glomerular filtration: rate 41.4 mL/min/m2) enrolled in the study. Baseline LVH (left ventricular mass index >131 g/m2 [>100 g/m2 if female]) was present in 10.8% and prolonged QTc intervals (≥500 ms) in 1.5% of participants. One hundred thirty-eight (6.1%) participants died during the study. In generalized mixed-effects regression, each unit increase in the natural log of FGF23 - but not LVH - predicted an odds ratio of 1.76 (1.15, 2.70, p = 0.009) for prolonged QTc intervals independently of 15 other covariates. Mediation analysis showed that only 13% of FGF23's total effect on prolonged QTc intervals was mediated by LVH. Patients with prolonged QTc intervals had higher unadjusted (log rank p < 0.001) and adjusted (hazard ratio: 2.06 [1.08, 3.92, p = 0.028]) mortality rates than those with QTc intervals <500 ms.

DISCUSSION

QTc interval prolongation ≥500 ms was prospectively associated with FGF23 independently of LVH and with increased mortality risk in patients with predialysis CKD.

Elevated serum FGF21 is an independent predictor for adverse events in hemodialysis patients from two large centers: a prospective cohort study

Introduction: We explored the relationship and the predictive value of serum fibroblast growth factor 21 (FGF21) with all-cause mortality, major adverse cardiovascular events (MACEs) and pneumonia in hemodialysis (HD) patients.Methods: A total of 388 Chinese HD patients from two HD centers were finally enrolled in this prospective cohort study (registration number: ChiCTR 1900028249) between January 2018 and December 2018. Serum FGF21 was detected. Patients were followed up with a median period of 47 months to record the MACEs and pneumonia until death or 31 December 2022.Results: The incidence of all-cause mortality, MACEs and pneumonia in HD patients were 20.6%, 29.6%, and 34.8%, respectively. The optimal cutoffs for FGF21 to predict all-cause mortality, MACEs and pneumonia were 437.57 pg/mL, 216.99 pg/mL and 112.79 pg/mL. Multivariate Cox regression analyses showed that FGF21, as a categorical variable, was an independent predictor for all-cause mortality, MACEs and pneumonia (HR, 3.357, 95% CI, 2.128-5.295, p < 0.001; HR, 1.575, 95% CI, 1.046-2.371, p = 0.029; HR, 1.784; 95% CI, 1.124-2.830; p = 0.014, respectively). The survival nomogram, MACEs-free survival nomogram and pneumonia-free survival nomogram based on FGF21 constructed for individualized assessment of HD patients had a high C-index with 0.841, 0.706 and 0.734.Conclusion: Higher serum FGF21 is an independent predictor of all-cause mortality, MACEs and pneumonia in HD patients.

Determination of FGF23 Levels for the Diagnosis of FGF23-Mediated Hypophosphatemia

Fibroblast growth factor-23 (FGF23) measurement is a critical tool in the evaluation of patients with disordered phosphate homeostasis. Available laboratory reference ranges for blood FGF23 were developed using samples from normophosphatemic individuals. Reliance on such values can lead to misdiagnosis in patients with FGF23-mediated hypophosphatemia, such as X-linked hypophosphatemia (XLH) and tumor-induced osteomalacia (TIO), in whom pathology-driving FGF23 levels can be in the "normal range." To determine FGF23 levels that are diagnostic for the identification of patients with FGF23-mediated hypophosphatemic disorders, we studied 149 patients with various disorders of FGF23-mediated and FGF23-independent hypophosphatemia and defined cut-off levels for both intact FGF23 (iFGF23) and C-terminal FGF23 (cFGF23) that can accurately distinguish between FGF23-mediated and FGF23-independent hypophosphatemia. In addition, to demonstrate the relationship between FGF23 and phosphate across the spectrum of human physiology, we assessed blood levels of FGF23 and phosphate in 434 patients with various forms of hypophosphatemia, hyperphosphatemia, and normophosphatemia. An intact FGF23 cut point of 27 pg/mL was 100% sensitive and specific in distinguishing FGF23-mediated from FGF23-independent hypophosphatemia, and a cFGF23 cut point of 90 RU/mL was 100% sensitive and specific in distinguishing specifically TIO from FGF23-independent hypophosphatemia. There was overlap in the cFGF23 range of 45-90 RU/mL between genetic forms of FGF23 excess and FGF23-independent hypophosphatemia, substantiating the superiority of iFGF23 over cFGF23 in making the diagnosis of FGF23-mediated hypophosphatemia. In this cohort, using the laboratory upper limit of normal for cFGF23 (180 RU/mL) would result in a misdiagnosis in more than half of patients with FGF23-mediated hypophosphatemia. In this, the largest study of FGF23 in chronic hypophosphatemia to date, we established iFGF23 and cFGF23 cut-off values to assist in the evaluation and diagnosis of hypophosphatemic conditions. © 2022 American Society for Bone and Mineral Research (ASBMR). This article has been contributed to by US Government employees and their work is in the public domain in the USA.

FGF21 response to sucrose is associated with BMI and dorsal striatal signaling in humans

OBJECTIVE

This study examined associations between BMI and dietary sugar intake with sucrose-induced fibroblast growth factor 21 (FGF21) and whether circulating FGF21 is associated with brain signaling following sucrose ingestion in humans.

METHODS

A total of 68 adults (29 male; mean [SD), age 23.2 [3.8] years; BMI 27.1 [4.9] kg/m² ) attended visits after a 12-hour fast. Plasma FGF21 was measured at baseline and at 15, 30, and 120 minutes after sucrose ingestion (75 g in 300 mL of water). Brain cerebral blood flow responses to sucrose were measured using arterial spin labeling magnetic resonance imaging.

RESULTS

Higher circulating FGF21 levels were associated with reduced blood flow in the striatum in response to sucrose (β = -7.63, p = 0.03). This association was greatest among persons with healthy weight (β = -15.70, p = 0.007) and was attenuated in people with overweight (β = -4.00, p = 0.63) and obesity (β = -12.45, p = 0.13). BMI was positively associated with FGF21 levels in response to sucrose (β = 0.53, p = 0.02). High versus low dietary sugar intake was associated with greater FGF21 responses to acute sucrose ingestion in individuals with healthy weight (β = 8.51, p = 0.04) but not in individuals with overweight or obesity (p > 0.05).

CONCLUSIONS

These correlative findings support evidence in animals showing that FGF21 acts on the brain to regulate sugar consumption through a negative feedback loop.

Non-Alcoholic Fatty Liver Disease in Long-Term Type 2 Diabetes: Role of rs738409 PNPLA3 and rs499765 FGF21 Polymorphisms and Serum Biomarkers

Fibroblast growth factor 21 (FGF21) signaling and genetic factors are involved in non-alcoholic fatty liver disease (NAFLD) pathogenesis. However, these factors have rarely been studied in type 2 diabetes mellitus (T2D) patients from admixed populations such as in those of Brazil. Therefore, we aimed to evaluate rs738409 patanin-like phospholipase domain-containing protein (PNPLA3) and rs499765 FGF21 polymorphisms in T2D, and their association with NAFLD, liver fibrosis, and serum biomarkers (FGF21 and cytokeratin 18 levels). A total of 158 patients were included, and the frequency of NAFLD was 88.6%, which was independently associated with elevated body mass index. Significant liver fibrosis (≥F2) was detected by transient elastography (TE) in 26.8% of NAFLD patients, and was independently associated with obesity, low density lipoprotein, and gamma-glutamyl transferase (GGT). PNPLA3 GG genotype and GGT were independently associated with cirrhosis. PNPLA3 GG genotype patients had higher GGT and AST levels; PNPLA3 GG carriers had higher TE values than CG patients, and FGF21 CG genotype patients showed lower gamma-GT values than CC patients. No differences were found in serum values of FGF21 and CK18 in relation to the presence of NAFLD or liver fibrosis. The proportion of NAFLD patients with liver fibrosis was relevant in the present admixed T2D population, and was associated with PNPLA3 polymorphisms.

Hepatocyte-specific fibroblast growth factor 21 overexpression ameliorates high-fat diet-induced obesity and liver steatosis in mice

Fibroblast growth factor (FGF) 21 is an endocrine growth factor mainly secreted by the liver in response to a ketogenic diet and alcohol consumption. FGF21 signaling requires co-receptor β-klotho (KLB) co-acting with FGF receptors, which has pleiotropic metabolic effects, including induced hepatic fatty acid oxidation and ketogenesis, in human and animal models of obesity. We examined the hepatocyte-specific enhancer/promoter of FGF21 expression plasmids in high-fat diet-fed mice for 12 weeks. Hydrodynamic injection for FGF21 delivery every 6 weeks sustained high circulating levels of FGF21, resulting in marked reductions in body weight, epididymal fat mass, insulin resistance, and liver steatosis. FGF21-induced lipolysis in the adipose tissue enabled the liver to be flooded with fat-derived FFAs. The hepatic expression of Glut2 and Bdh1 was upregulated, whereas that of gluconeogenesis-related genes, G6p and Pepck, and lipogenesis-related genes, Srebp-1 and Srebp-2, was significantly suppressed. FGF21 induced the phosphorylation of AMPK at Thr172 and Raptor at ser792 and suppressed that of mTOR at ser2448, which downregulated mTORC1 signaling and reduced IRS-1 phosphorylation at ser1101. Finally, in the skeletal muscle, FGF21 increased Glut4 and Mct2, a membrane protein that acts as a carrier for ketone bodies. Enzymes for ketone body catabolism (Scot) and citrate cycle (Cs, Idh3a), and a marker of regenerating muscle (myogenin) were also upregulated via increased KLB expression. Thus, FGF21-induced lipolysis was continuously induced by a high-fat diet and fat-derived FFAs might cause liver damage. Hepatic fatty acid oxidation and ketone body synthesis may act as hepatic FFAs' disposal mechanisms and contribute to improved liver steatosis. Liver-derived ketone bodies might be used for energy in the skeletal muscle. The potential FGF21-related crosstalk between the liver and extraliver organs is a promising strategy to prevent and treat metabolic syndrome-related nonalcoholic steatohepatitis.

Fibroblast Growth Factor 21 as a Marker of Prediabetes in Patients with Non-alcoholic Fatty Liver Disease

BACKGROUND

Fibroblast growth factor 21 is a peptide primarily secreted by the liver in response to peroxisome proliferator-activated receptor-α activation which plays an important role in regulating carbohydrate and lipid metabolism. This study investigated the association between fibroblast growth factor 21 and prediabetes in obese patients with non-alcoholic fatty liver disease in adult population.

METHODS

A total of 85 obese non-alcoholic fatty liver disease patients without (n = 49) and with prediabetes (n = 36) were included. Serum fibroblast growth factor 21 levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Higher fibroblast growth factor 21 serum levels were observed in patients with prediabetes, metabolic syndrome, dyslipidemia, and insulin resistance. There were significant correlations between fibroblast growth factor 21 and waist-to-stature ratio, visceral adiposity index, triglycerides, very low-density lipoproteins, alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT), Quantitative Insulin Sensitivity Check Index, and Stumvoll index of insulin sensitivity. Fibroblast growth factor 21 level ≥320 pg/mL was associated with a 4.2-fold higher risk of prediabetes and ≥270 pg/mL for metabolic syndrome approximately 4 times.

CONCLUSION

Fibroblast growth factor 21 is associated with increased risk for prediabetes, metabolic syndrome, and insulin resistance in obese patients with non-alcoholic fatty liver disease.

Association of serum fibroblast growth factor 21 with diabetic complications and insulin dose in patients with type 1 diabetes mellitus

Introduction

Fibroblast growth factor (FGF) 21 is an important regulator of glycemic control, but the association between circulating FGF21 and diabetic complications is poorly understood. Moreover, basal FGF21 secretion, especially in response to insulin dose, in patients with type 1 diabetes mellitus (T1DM), has not been well examined. Therefore, this study aimed to determine the association of circulating FGF21 levels with diabetic complications and insulin dosage in middle-aged and elderly patients with T1DM.

Materials and methods

A total of 127 middle-aged and elderly patients with T1DM, including 68 patients with diabetic complications, and 106 non-diabetic individuals were analyzed in this cross-sectional study. Information on demographic characteristics and T1DM was extracted from their electronic medical records. Serum FGF21 levels were determined using ELISA.

Results

Serum FGF21 levels were significantly lower in T1DM patients (75.2 [37.4–135.1] pg/mL) than in non-diabetic participants (151.6 [92.0–224.6] pg/mL; P < 0.001). No diabetic complications were associated with serum FGF21 concentrations. Both basal and bolus insulin doses were significantly and positively correlated with serum FGF21 levels (P < 0.05). Stepwise multiple regression analysis showed that FGF21 level was associated with age and body mass index (P < 0.05), while the basal insulin dose was an independent positive predictor of serum FGF21 levels (β = 0.197, P = 0.032).

Conclusions

Circulating FGF21 levels are reduced in patients with T1DM; however, they are not associated with diabetic complications. In addition, aging, obesity, and insulin dosage are positive determinants of circulating FGF21.

Plasma FGF21 concentrations and spontaneous self-selection of protein suggest that 15% protein in the diet may not be enough for male adult rats

Protein requirement has been determined at 10%-15% energy. Under dietary self-selection, rats ingest 25%-30% energy as protein and regulate FGF21 (a hormone signaling protein deficiency) to levels lower than those measured with a 15% protein (15P) diet. Our hypothesis is that if a 15P diet was indeed sufficient to ensure protein homeostasis, it is probably a too low protein level to ensure optimal energy homeostasis. Adult male Wistar rats were used in this study. The first objective was to determine the changes in food intake, body composition, and plasma FGF21, IGF-1, and PYY concentrations in rats fed 8P, 15P, 30P, 40P, or 50P diets. The second was to determine whether the FGF21 levels measured in the rats were related to spontaneous protein intake. Rats were fed a 15P diet and then allowed to choose between a protein diet and a protein-free diet. Food intake and body weight were measured throughout the experiments. Body composition was determined at different experimental stages. Plasma samples were collected to measure FGF21, IGF-1, and PYY concentrations. A 15P diet appears to result in higher growth than that observed with the 30P, 40P, and 50P diets. However, the 15P diet probably does not provide optimal progression of body composition owing to a tendency of 15P rats to fix more fat and energy in the body. The variable and higher concentrations of FGF21 in the 15P diet suggest a deficit in protein intake, but this does not appear to be a parameter reflecting the adequacy of protein intake relative to individual protein requirements.NEW & NOTEWORTHY Under dietary self-selection, rats choose to ingest 25%-30% of energy as protein, a value higher than the protein requirement (10%-15%). According to our results, this higher spontaneous intake reflects the fact that rats fed a 15% protein diet, compared with high-protein diets, tend to bind more fat and have higher concentrations of FGF21, a hormone signaling protein deficiency. A 15% protein diet appears to be sufficient for protein homeostasis but not for optimal energy homeostasis.

The Regulatory Role of the Central and Peripheral Serotonin Network on Feeding Signals in Metabolic Diseases

Central and peripheral serotonin (5-hydroxytryptamine, 5-HT) regulate feeding signals for energy metabolism. Disruption of central 5-HT signaling via 5-HT2C receptors (5-HT2CRs) induces leptin-independent hyperphagia in mice, leading to late-onset obesity, insulin resistance, and impaired glucose tolerance. 5-HT2CR mutant mice are more responsive than wild-type mice to a high-fat diet, exhibiting earlier-onset obesity and type 2 diabetes. High-fat and high-carbohydrate diets increase plasma 5-HT and fibroblast growth factor-21 (FGF21) levels. Plasma 5-HT and FGF21 levels are increased in rodents and humans with obesity, type 2 diabetes, and non-alcohol fatty liver diseases (NAFLD). The increases in plasma FGF21 and hepatic FGF21 expression precede hyperinsulinemia, insulin resistance, hyperglycemia, and weight gain in mice fed a high-fat diet. Nutritional, pharmacologic, or genetic inhibition of peripheral 5-HT synthesis via tryptophan hydroxylase 1 (Tph1) decreases hepatic FGF21 expression and plasma FGF21 levels in mice. Thus, perturbing central 5-HT signaling via 5-HT2CRs alters feeding behavior. Increased energy intake via a high-fat diet and/or high-carbohydrate diet can upregulate gut-derived 5-HT synthesis via Tph1. Peripheral 5-HT upregulates hepatic FGF21 expression and plasma FGF21 levels, leading to metabolic diseases such as obesity, insulin resistance, type 2 diabetes, and NAFLD. The 5-HT network in the brain–gut–liver axis regulates feeding signals and may be involved in the development and/or prevention of metabolic diseases.

Phosphaturic mesenchymal tumor: An underdiagnosed rare entity

Tumor-induced osteomalacia is a paraneoplastic syndrome resulting in renal phosphate wasting and decreased bone mineralization. Phosphaturic mesenchymal tumors represent a rare etiology of tumor-induced osteomalacia. They are exceptionally rare, probably accounting for < 0.01% of all soft tissue tumors. Most PMTs present as small inapparent lesions that require very careful clinical examination and radionucleotide scan for localization. Here we describe a case in a 65 years old woman with recurrent multiple bone fractures and subsequent detection of a tumor involving right femur and adjacent soft tissue, low phosphate level and elevated serum Fibroblast growth factor-23 (FGF-23).

The fibroblast growth factor 21 concentration in children with mitochondrial disease does not depend on the disease stage, but rather on the disease genotype

ABSTRACT

The fibroblast growth factor 21 (FGF21) is a new biomarker of mitochondrial diseases (MD). FGF21 concentration may be used to define the severity of mitochondrial disease.

AIM OF THE STUDY

The study objective was to verify if the FGF21 concentration in paediatric patients with MD was correlated with the disease severity and stage and to assess the correlation between FGF21 levels and the genetic background of MD.

MATERIAL AND METHODS

The disease stage in MD subjects was determined on the basis of the International Paediatric Mitochondrial Disease Scale (IPMDS) and the concentrations of FGF21, lactic and pyruvic acids, alanine and creatine kinase in serum were assessed in those patients.

RESULTS

The median age of children with MD (n = 32) was 33 months (range: 2-213), in the control group (n = 21) the median age was 42 months (range: 8-202). The concentrations of FGF21, lactic acid and pyruvic acid were higher in MD patients than in the control group. No correlation between the disease severity (IPMDS) and serum FGF21 concentration was found. The FGF21 concentration was higher in patients whose MD resulted from nuclear gene damage (nDNA), median FGF21 = 1022 (84-8873) pg/ml, than in patients with MD resulting from mitochondrial damage (mtDNA), median FGF21 = 736 (188-2906) pg/ml, or with an abnormal variant in the PDHA1 gene, median FGF21 = 58 (25-637) pg/ml.

CONCLUSIONS

There is no correlation between the stage of MD and FGF21 level. Higher FGF21 values are seen in patients whose MD results from an abnormal nDNA variant rather than mtDNA damage.

Mice with high FGF21 serum levels had a reduced preference for morphine and an attenuated development of acute antinociceptive tolerance and physical dependence

Because of increased opioid misuse, there is a need to identify new targets for minimizing opioid tolerance, and physical and psychological dependence. Previous studies showed that fibroblast growth factor 21 (FGF21) decreased alcohol and sweet preference in mice. In this study, FGF21-transgenic (FGF21-Tg) mice, expressing high FGF21 serum levels, and wildtype (WT) C57BL/6J littermates were treated with morphine and saline to determine if differences exist in their physiological and behavioral responses to opioids. FGF21-Tg mice displayed reduced preference for morphine in the conditioned place preference assay compared to WT littermates. Similarly, FGF21-Tg mice had an attenuation of the magnitude and rate of acute morphine antinociceptive tolerance development, and acute and chronic morphine physical dependence, but exhibited no change in chronic morphine antinociceptive tolerance. The ED50 values for morphine-induced antinociception in the 55 °C hot plate and the 55 °C warm-water tail withdrawal assays were similar in both strains of mice. Likewise, FGF21-Tg and WT littermates had comparable responses to morphine-induced respiratory depression. Overall, FGF21-Tg mice had a decrease in the development of acute analgesic tolerance, and the development of physical dependence, and morphine preference. FGF21 and its receptor have therapeutic potential for reducing opioid withdrawal symptoms and craving, and augmenting opioid therapeutics for acute pain patients to minimize tolerance development.

Association of serum fibroblast growth factor 21 with kidney function in a population-based Chinese cohort

Fibroblast growth factor 21 (FGF21) plays a role in kidney disease. Circulating FGF21 levels are associated with kidney function and progression in patients with type 2 diabetes (T2D). However, the association between FGF21 and kidney function in the general population is still lacking. The aim of this study was to determine the association between FGF21 and kidney function and its progression in a Chinese cohort.A total of 2425 participants from a population-based survey of diabetes and metabolic syndrome in Pinggu, Beijing, were included in the baseline analysis. After a median follow-up of 12 months, 2402 participants with baseline estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m2 were analyzed in the longitudinal study. The progression of kidney function was defined as an eGFR decline exceeding 3.3% per year. Serum FGF21 levels were measured using an enzyme-linked immunosorbent assay at baseline.Male sex, body mass index (BMI), homeostasis model assessment of insulin resistance, higher levels of low-density lipoprotein cholesterol (LDL-c), uric acid, and FGF21 were associated with increased odds of a lower eGFR at baseline. The association of FGF21 with lower eGFR was independent of all the potential confounders in multivariable logistic regression (odds ratio, 1.005; 95% confidence interval 1.002-1.008). However, FGF21 was not associated with eGFR decline in the longitudinal analysis (odds ratio, 1.000; 95% confidence interval 0.998-1.001).Increased serum FGF21 levels were independently associated with lower eGFR in this nonmedicated general population. FGF21 could be a biomarker of kidney function in the general population.

The combination of soluble tumor necrosis factor receptor type 1 and fibroblast growth factor 21 exhibits better prediction of renal outcomes in patients with type 2 diabetes mellitus

PURPOSE

Numerous biomarkers of diabetic kidney disease (DKD) are associated with renal prognosis but head-to-head comparisons are lacking. This study aimed to examine the association of soluble tumor necrosis factor receptor type 1 (sTNFR1), fibroblast growth factor 21 (FGF-21), endocan, N-terminal pro-brain natriuretic peptide (NT-pro-BNP), and renal outcomes of patients with or without clinical signs of DKD.

METHODS

A total of 312 patients were enrolled in a prospective observational study that excluded individuals with estimated glomerular filtration rates (eGFR) < 30 mL/min/1.73 m². Composite renal outcomes included either a > 30% decline in eGFR and worsening albuminuria or both from consecutive tests of blood/urine during a 3.5-year follow-up period.

RESULTS

Higher sTNFR1 and FGF-21, rather than endocan and NT-pro-BNP, levels were associated with renal outcomes but the significance was lost after adjusting for confounders. However, sTNFR1 levels ≥ 9.79 pg/dL or FGF-21 levels ≥ 1.40 pg/dL were associated with renal outcomes after adjusting for the confounders (hazard ration [HR] 2.76, 95% confidence interval [CI] 1.36-5.60, p = 0.005 for sTNFR1 level; HR 1.95, 95% CI 1.03-3.69, p = 0.03 for FGF-21 level). The combination of both levels exhibited even better association with renal outcomes than did either one alone (adjusted HR 4.45, 95% CI 1.86-10.65, p = 0.001). The results were consistent among patients with preserved renal function and normoalbuminuria.

CONCLUSION

Both sTNFR1 and FGF-21 levels were associated with renal outcomes of in patients with type 2 diabetes, and the combination of the abovementioned markers exhibits better predictability.

Dominant factors of the phosphorus regulatory network differ under various dietary phosphate loads in healthy individuals

BACKGROUND

The purpose of this study was to explore the contribution of each factor of the phosphorus metabolism network following phosphorus diet intervention via Granger causality analysis.

METHODS

In this study, a total of six healthy male volunteers were enrolled. All participants sequentially received regular, low-, and high-phosphorus diets. Consumption of each diet lasted for five days, with a 5-day washout period between different diets. Blood and urinary samples were collected on the fifth day of consumption of each diet at 9 time points (00:00, 04:00, 08:00, 10:00, 12:00, 14:00, 16:00, 20:00, 24:00) for measurements of serum levels of phosphate, calcium, PTH, FGF23, BALP, α-Klotho, and 1,25 D and urinary phosphorus excretion. Granger causality and the centrality of the above variables in the phosphorus network were analyzed by pairwise panel Granger causality analysis using the time-series data.

RESULTS

The mean age of the participants was 28.5 ± 2.1 years. By using Granger causality analysis, we found that the α-Klotho level had the strongest connection with and played a key role in influencing the other variables. In addition, urinary phosphorus excretion was frequently regulated by other variables in the network of phosphorus metabolism following a regular phosphorus diet. After low-phosphorus diet intervention, serum phosphate affected the other factors the most, and the 1,25 D level was the main outcome factor, while urinary phosphorus excretion was the most strongly associated variable in the network of phosphorus metabolism. After high-phosphorus diet intervention, FGF23 and 1,25 D played a more critical role in active regulation and passive regulation in the Granger causality analysis.

CONCLUSIONS

Variations in dietary phosphorus intake led to changes in the central factors involved in phosphorus metabolism.

Fibroblast growth factor 21 attenuates salt-sensitive hypertension-induced nephropathy through anti-inflammation and anti-oxidation mechanism

BACKGROUND

Patients with salt-sensitive hypertension are often accompanied with severe renal damage and accelerate to end-stage renal disease, which currently lacks effective treatment. Fibroblast growth factor 21 (FGF21) has been shown to suppress nephropathy in both type 1 and type 2 diabetes mice. Here, we aimed to investigate the therapeutic effect of FGF21 in salt-sensitive hypertension-induced nephropathy.

METHODS

Changes of FGF21 expression in deoxycorticosterone acetate (DOCA)-salt-induced hypertensive mice were detected. The influence of FGF21 knockout in mice on DOCA-salt-induced nephropathy were determined. Recombinant human FGF21 (rhFGF21) was intraperitoneally injected into DOCA-salt-induced nephropathy mice, and then the inflammatory factors, oxidative stress levels and kidney injury-related indicators were observed. In vitro, human renal tubular epithelial cells (HK-2) were challenged by palmitate acid (PA) with or without FGF21, and then changes in inflammation and oxidative stress indicators were tested.

RESULTS

We observed significant elevation in circulating levels and renal expression of FGF21 in DOCA-salt-induced hypertensive mice. We found that deletion of FGF21 in mice aggravated DOCA-salt-induced nephropathy. Supplementation with rhFGF21 reversed DOCA-salt-induced kidney injury. Mechanically, rhFGF21 induced AMPK activation in DOCA-salt-treated mice and PA-stimulated HK-2 cells, which inhibited NF-κB-regulated inflammation and Nrf2-mediated oxidative stress and thus, is important for rhFGF21 protection against DOCA-salt-induced nephropathy.

CONCLUSION

These findings indicated that rhFGF21 could be a promising pharmacological strategy for the treatment of salt-sensitive hypertension-induced nephropathy.

The serum fibroblast growth factor 21 is correlated with retinopathy in patients with type 2 diabetes mellitus

AIMS

despite advances in blood glucose control, the incidence of sight loss has not decreased in patients with diabetes. Several growth factors have been suggested as factors associated with diabetic retinopathy pathogenesis. In the current cross-sectional study, we examined the relationship between FGF21 and retinopathy as a microvascular complication of diabetes.

METHODS

Adult patients with type 2 diabetes mellitus (T2DM); were recruited and evaluated for retinopathy. Different clinical and biochemical factors, such as FGF21 were assessed and compared between groups.

RESULTS

91 T2DM patients with retinopathy, 93 T2DM patients without retinopathy, and 86 healthy control subjects were recruited. FGF21 was significantly different between the three groups (P<0.001). In the multivariate logistic regression model obesity, cholesterol, HbA1c, and FGF21 were associated with diabetic retinopathy. ROC curve analysis was used for establishing a cut-off FGF21 concentration to predict diabetic retinopathy. The area under the curve in this model was 0.992. The best cut-off point for predicting retinopathy based on FGF21 was greater than 312 pg/ml, with a sensitivity of 97.80% and specificity of 96.77%.

CONCLUSION

FGF21 was associated with diabetic retinopathy and can be suggested as a surrogate diagnostic marker in the diagnosis of this state.

Non-Alcoholic Steatohepatitis Severity Associates with FGF21 Level and Kidney Glucose Uptake

Background: Nonalcoholic steatohepatitis (NASH) is a severe form of fatty liver disease that has been shown to be associated with chronic kidney disease (CKD). Mechanism for the association of NASH with CKD remains unclear. In this study, we examined the association between NASH severity and kidney glucose uptake and the liver-secreted signaling molecule fibroblast growth factor 21 (FGF21). Methods: Kinetic parameters for kidney glucose transport rate (K₁) and standardized uptake value (SUV) were determined using dynamic positron emission tomography after injection of ¹⁸F-fluorodeoxyglucose. Liver biopsies were scored for NASH activity (inflammation and ballooning), fibrosis, and steatosis FGF21 was measured from fasting serum samples. Patients were categorized by liver biopsy and multivariate analyses were performed to evaluate the associations. Results: Of 41 NASH patients 73% were females, 71% white, 51% with steatosis ≥2, 39% with NASH activity ≥4 and fibrosis ≥3. With severe NASH activity, kidney SUV significantly increased even when adjusted for underlying insulin-resistant (IR) state. Kidney K₁ decreased significantly in higher liver activity in unadjusted models but not when adjusted for IR. FGF21 decreased with severe liver activity in adjusted models (P < 0.05) and associated with kidney K1 but not SUV. Conclusion: Our pilot data indicate that kidney glucose metabolism associates with NASH activity and FGF21 levels, suggesting a potential mechanism to NASH-induced CKD. Clinical Trials.gov ID: NCT02754037.

Does FGF21 Mediate the Potential Decrease in Sweet Food Intake and Preference Following Bariatric Surgery?

The liver-derived hormone fibroblast growth factor 21 (FGF21) has recently been linked to preference for sweet-tasting food. We hypothesized, that surgery-induced changes in FGF21 could mediate the reduction in sweet food intake and preference following bariatric surgery. Forty participants (35 females) with severe obesity (BMI ≥ 35 kg/m²) scheduled for roux-en-y gastric bypass (n = 30) or sleeve gastrectomy (n = 10) were included. Pre- and postprandial responses of intact plasma FGF21 as well as intake of sweet-tasting food assessed at a buffet meal test, the hedonic evaluation of sweet taste assessed using an apple juice with added sucrose and visual analog scales, and sweet taste sensitivity were assessed before and 6 months after bariatric surgery. In a cross-sectional analysis pre-surgery, pre- and postprandial intact FGF21 levels were negatively associated with the hedonic evaluation of a high-sucrose juice sample (p = 0.03 and p = 0.02). However, no changes in pre- (p = 0.24) or postprandial intact FGF21 levels were found 6 months after surgery (p = 0.11), and individual pre- to postoperative changes in pre- and postprandial intact FGF21 levels were not found to be associated with changes in intake of sweet foods, the hedonic evaluation of sweet taste or sweet taste sensitivity (all p ≥ 0.10). In conclusion, we were not able to show an effect of bariatric surgery on circulating FGF21, and individual postoperative changes in FGF21 were not found to mediate an effect of surgery on sweet food intake and preference.

Circulating fibroblast growth factor 21 as a potential biomarker for missed abortion in humans

OBJECTIVE

To investigate whether serum levels of fibroblast growth factor 21 (FGF21) and fatty acid-binding protein-4 (FABP4) are associated with missed abortion (MA) in humans.

DESIGN

Cross-sectional study.

SETTING

University-affiliated hospital.

PATIENT(S)

Patients with MA at 8-12 weeks of gestation.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURES(S)

Serum levels of FGF21 and FABP4 were tested by enzyme-linked immunosorbent assay. Placental samples were collected during dilation and curettage surgery, and the expression of FGF21 and its related genes were measured using quantitative polymerase chain reaction.

RESULT(S)

In the discovery cohort, 78 patients with MA and 79 healthy pregnant women matched for maternal age and body mass index were nested from a prospective cohort. Circulating levels of FGF21 and FABP4 were significantly and independently elevated in patients with MA relative to the levels in the healthy controls. A single measurement of FGF21 serum level effectively discriminated MA with an area under the receiver operating characteristics curve of 0.80 (95% confidence interval: 0.73-0.87). Importantly, in our external validation cohort that comprised subjects with MA (n = 34) or induced abortion (n = 27), the FGF21 serum levels achieved an area under the receiver operating characteristics curve of 0.85 (95% confidence interval: 0.75-0.96) when identifying those with MA. Nevertheless, expression of FGF21 in the placenta was not associated with its serum concentration. Placental tissues from patients with MA exhibited impaired FGF21 signaling.

CONCLUSION(S)

Our results suggested that serum levels of FGF21 and FABP4 were associated with MA. Circulating FGF21 may serve as a potential biomarker for the recognition of MA.

The Mitochondrial Biomarkers FGF-21 and GDF-15 in Patients with Episodic and Chronic Migraine

Mitochondrial processes may play a role in the pathophysiology of migraine. Serum levels of two biomarkers, Fibroblast-growth-factor 21 (FGF-21) and Growth-differentiation-factor 15 (GDF-15), are typically elevated in patients with mitochondrial disorders. The study investigated whether the presence of migraine may influence FGF-21 and GDF-15 serum levels considering vascular and metabolic disorders as possible confounders. A cross-sectional study in two headache centers was conducted analyzing GDF-15 and FGF-21 serum concentration in 230 patients with episodic and chronic migraine compared to a control group. Key clinical features of headache were evaluated, as well as health-related life quality, anxiety and depression using SF-12 and HADS-questionnaires. Elevated GDF-15 values were detected in the migraine group compared to the control group (506.65 ± 275.87 pg/mL vs. 403.34 ± 173.29 pg/mL, p < 0.001, Mann–Whitney U test). A strong correlation between increasing age and higher GDF-15 levels was identified (p < 0.001, 95%-CI elevation of GDF-15 per year 5.246–10.850 pg/mL, multiple linear regression). Mean age was different between the groups, and this represents a confounding factor of the measurements. FGF-21 levels did not differ between migraine patients and controls (p = 0.635, Mann–Whitney U test) but were significantly influenced by increasing BMI (p = 0.030, multiple linear regression). Neither biomarker showed correlation with headache frequency. Higher FGF-21 levels were associated with a higher mean intensity of headache attacks, reduced health-related life quality and anxiety. When confounding factors were considered, increased serum levels of FGF-21 and GDF-15 were not detected in migraine patients. However, the results show an age-dependence of GDF-15 in migraine patients, and this should be considered in future studies. Similar findings apply to the relationship between FGF-21 and BMI. Previous studies that did not adjust for these factors should be interpreted with caution.

Fibroblast Growth Factor 21 as a Potential Biomarker for Improved Locomotion and Olfaction Detection Ability after Weight Reduction in Obese Mice

Obesity is one of the most challenging diseases of the 21st century and is accompanied by behavioural disorders. Exercise, dietary adjustments, or time-restricted feeding are the only successful long-term treatments to date. Fibroblast growth factor 21 (FGF21) plays a key role in dietary regulation, but FGF21 resistance is prevalent in obesity. The aim of this study was to investigate in obese mice whether weight reduction leads to improved behaviour and whether these behavioural changes are associated with decreased plasma FGF21 levels. After establishing a model for diet-induced obesity, mice were subjected to three different interventions for weight reduction, namely dietary change, treadmill exercise, or time-restricted feeding. In this study, we demonstrated that only the combination of dietary change and treadmill exercise affected all parameters leading to a reduction in weight, fat, and FGF21, as well as less anxious behaviour, higher overall activity, and improved olfactory detection abilities. To investigate the interrelationship between FGF21 and behavioural parameters, feature selection algorithms were applied designating FGF21 and body weight as one of five highly weighted features. In conclusion, we concluded from the complementary methods that FGF21 can be considered as a potential biomarker for improved behaviour in obese mice after weight reduction.

Fibroblast Growth Factor 23 and Incident Cardiovascular Disease and Mortality in Middle-Aged Adults

Background Higher circulating fibroblast growth factor 23 (FGF23) associates with greater risk of cardiovascular disease (CVD) and mortality in older adults. The association of FGF23 with cardiovascular outcomes in younger populations has been incompletely explored. Methods and Results We measured C-terminal FGF23 (cFGF23) and intact FGF23 (iFGF23) in 3151 middle-aged adults (mean age, 45±4) who participated in the year 20 examination of the CARDIA (Coronary Artery Risk Development in Young Adults) study. We used separate Cox proportional hazards models to examine the associations of cFGF23 and iFGF23 with incident CVD and mortality, adjusting models sequentially for sociodemographic, clinical, and laboratory factors. A total of 157 incident CVD events and 135 deaths occurred over a median 7.6 years of follow-up (interquartile range, 4.1-9.9). In fully adjusted models, there were no statistically significant associations of FGF23 with incident CVD events (hazard ratio per doubling of cFGF23: 1.14, 95%CI 0.97,1.34; iFGF23: 0.76, 95%CI 0.57,1.02) or all-cause mortality (hazard ratio per doubling of cFGF23, 1.17; 95% CI, 1.00-1.38; iFGF23, 0.86; 95% CI, 0.64-1.17). In analyses stratified by CVD subtypes, higher cFGF23 was associated with greater risk of heart failure hospitalization (hazard ratio per doubling of cFGF23, 1.52; 95% CI, 1.18-1.96) but not coronary heart disease or stroke, whereas iFGF23 was not associated with CVD subtypes in any model. Conclusions In middle-aged adults with few comorbidities, higher cFGF23 and iFGF23 were not independently associated with greater risk of CVD events or death. Higher cFGF23 was independently associated with greater risk of heart failure hospitalization.

Intestinal Phosphorus Absorption in Moderate CKD and Healthy Adults Determined Using a Radioisotopic Tracer

BACKGROUND

Reducing intestinal phosphorus absorption is a cornerstone in CKD-MBD management. Yet, knowledge gaps include how CKD pathophysiology affects intestinal phosphorus absorption. In vivo rodent studies suggest that intestinal phosphorus absorption remains inappropriately normal in early-moderate CKD, despite declining 1,25-dihydroxyvitamin D (1,25D). We measured intestinal phosphorus absorption in patients with moderate CKD versus healthy adults using a direct radiotracer method.

METHODS

Patients with CKD and healthy adults matched for age, sex, and race were enrolled in this 8-day controlled diet study: the first 6 days outpatient and the final 2 days inpatient. Oral and intravenous doses of 33P and serial blood and urine sampling determined intestinal phosphorus absorption during the final 2 days. Secondary outcomes included fasting biochemistries and 24-hour urine phosphorus (uP).

RESULTS

In total, n=8 patients with CKD (eGFR=29-55 ml/min per 1.73 m2) and n=8 matched healthy controls completed the study. On a controlled diet, no difference in fractional intestinal phosphorus absorption was detected between patients with CKD and healthy adults (0.69 versus 0.62, respectively; P=0.52), and this was similar for 24-hour uP (884 versus 935 mg/d, respectively; P=0.70). Fractional intestinal phosphorus absorption was not significantly related to 24-hour uP. Patients with CKD had higher serum intact PTH and intact FGF23 and lower 1,25D. The relationship between 1,25D and fractional intestinal phosphorus absorption was not statistically significant.

CONCLUSIONS

Intestinal phosphorus absorption with typical dietary intake did not differ in patients with moderate CKD compared with controls, despite lower serum 1,25D levels. In this setting, a relationship between 24-hour uP and fractional or absolute intestinal absorption was not evident. Further investigation is needed to determine what factors influence intestinal phosphorus absorption in CKD and the apparent lack of compensation by the intestine to limit phosphorus absorption in the face of declining kidney function and reduced 1,25D. Whether this is evident across a range of dietary phosphorus intakes, as well as CKD severity, also needs to be determined.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Phosphorus Absorption in Healthy Adults and in Patients with Moderate Chronic Kidney Disease, NCT03108222.

Quantification of serum fibroblast growth factor-19 concentration in healthy dogs before and after feeding

OBJECTIVE

To measure serum fibroblast growth factor-19 (FGF-19) concentration and gallbladder volume in healthy dogs before and after feeding to determine whether serum FGF-19 concentration increases following gallbladder contraction and to assess FGF-19 stability in blood samples kept under different storage conditions after collection in tubes containing no anticoagulant or in serum separator tubes.

ANIMALS

10 healthy dogs of various ages and breeds (30 blood samples and 30 gallbladder volume measurements).

PROCEDURES

Serum FGF-19 concentration was measured with a commercially available ELISA. Gallbladder volume was determined ultrasonographically. Blood samples and gallbladder measurements were obtained from the dogs after food had been withheld for 12 hours (baseline) and at 1 and 3 hours after feeding. The stability of serum FGF-19 was assessed in samples collected in tubes containing no anticoagulant or in serum separator tubes and stored at -80°C for variable intervals or 4°C for 1 or 5 days.

RESULTS

Serum FGF-19 concentration was significantly increased from baseline at 1 and 3 hours after feeding. There was a significant decrease in gallbladder volume 1 hour after feeding, compared with baseline findings. Regardless of collection tube used, concentrations of FGF-19 in serum obtained from blood samples that were collected and immediately stored at -80°C differed significantly from concentrations in serum obtained from blood samples that had been collected and stored at 4°C for 5 days.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that postprandial gallbladder contraction results in increases of serum FGF-19 concentration in healthy dogs. Assessment of circulating FGF-19 concentration could be used to detect disruptions in the enterohepatic-biliary axis in dogs.

Associations of serum soluble klotho and fibroblast growth factor 23 with carotid artery calcification in patients undergoing continuous ambulatory peritoneal dialysis: A retrospective study

ABSTRACT

This study aimed to assess the associations of serum soluble klotho and fibroblast growth factor 23 (FGF-23) with the occurrence of carotid artery calcification. Peritoneal dialysis patients treated from June 2018 to June 2019 were retrospectively analyzed. They were divided into the carotid artery calcification and non-carotid artery calcification groups according to color Doppler ultrasound findings. Basic indicators in both groups were compared, and the influencing factors of carotid artery calcification were analyzed by logistic regression. Among the 73 continuous ambulatory peritoneal dialysis (CAPD) patients enrolled, 40 (54.8%) had carotid artery calcification. Significant differences were found in age (68.85 ± 7.45 vs 46.62 ± 5.51 years), dialysis time (8.15 ± 1.42 vs 6.02 ± 1.14 months), klotho amounts (325.56 ± 41.15 vs 436.65 ± 45.58 pg/mL) and FGF-23 levels (114.45 ± 15.56 vs 70.15 ± 12.23 pg/mL) between the carotid artery calcification and non-carotid artery calcification groups (all P < .001). The above factors were associated with carotid artery calcification occurrence in univariate analysis. Multivariate analysis showed that elevated age (odds ratio [OR] = 1.55, 95% confidence interval [CI] 1.13-1.74; P = .025) and FGF-23 (OR = 2.16, 95% CI 2.01-2.44; P = .042), and lower klotho (OR = 0.66, 95% CI 0.47-0.85; P = .036) were independent risk factors for carotid artery calcification in CAPD. Serum FGF-23 and age are risk factors for carotid artery calcification in patients with CAPD, whereas klotho is a protective factor.

Significance of serum FGF-23 for risk assessment of contrast-associated acute kidney injury and clinical outcomes in patients undergoing coronary angiography

Background

Fibroblast growth factor (FGF)-23 levels rise as kidney function declines. Whether elevated FGF-23 levels are associated with an increased risk for contrast-associated acute kidney injury (CA-AKI) and major adverse cardiovascular events (MACE) in patients undergoing coronary angiography remain uncertain.

Methods

In total, 492 patients receiving coronary angiography were enrolled. Their serum FGF-23 levels were measured before administration of contrast media. The occurrence of CA-AKI was defined as a rise in serum creatinine of 0.5 mg/dL or a 25% increase from the baseline value within 48 h after the procedure. All patients were followed up for at least 1 year or until the occurrence of MACE including death, nonfatal myocardial infarction (MI), and ischemic stroke.

Results

Overall, CA-AKI occurred in 41 (8.3%) patients. During a median follow-up of 2.6 years, there were 24 deaths, 3 nonfatal MIs, and 7 ischemic strokes. Compared with those in the lowest FGF-23 tertile, individuals in the highest FGF-23 tertile had a significantly higher incidence of CA-AKI (P < 0.001) and lower incidence of MACE-free survival (P = 0.001). In multivariate regression analysis, higher FGF-23 level was found to be independently associated with a graded risk for CA-AKI (OR per doubling, 1.90; 95% CI 1.48–2.44) and MACE (HR per doubling, 1.25; 95% CI 1.02–1.52).

Conclusions

Elevated FGF-23 levels were associated with an increased risk for CA-AKI and future MACE among patients undergoing coronary angiography. FGF-23 may play a role in early diagnosis of CA-AKI and predicting clinical outcomes after coronary angiography.

A phosphate and calcium-enriched diet promotes progression of 5/6-nephrectomy-induced chronic kidney disease in C57BL/6 mice

C57BL/6 mice are known to be rather resistant to the induction of experimental chronic kidney disease (CKD) by 5/6-nephrectomy (5/6-Nx). Here, we sought to characterize the development of CKD and its cardiac and skeletal sequelae during the first three months after 5/6-Nx in C57BL/6 mice fed a calcium- and phosphate enriched diet (CPD) with a balanced calcium/phosphate ratio. 5/6-NX mice on CPD showed increased renal fibrosis and a more pronounced decrease in glomerular filtration rate when compared to 5/6-Nx mice on normal diet (ND). Interestingly, despite comparable levels of serum calcium, phosphate, and parathyroid hormone (PTH), circulating intact fibroblast growth factor-23 (FGF23) was 5 times higher in 5/6-Nx mice on CPD, relative to 5/6-Nx mice on ND. A time course experiment revealed that 5/6-Nx mice on CPD developed progressive renal functional decline, renal fibrosis, cortical bone loss, impaired bone mineralization as well as hypertension, but not left ventricular hypertrophy. Collectively, our data show that the resistance of C57BL/6 mice to 5/6-Nx can be partially overcome by feeding the CPD, and that the CPD induces a profound, PTH-independent increase in FGF23 in 5/6-Nx mice, making it an interesting tool to assess the pathophysiological significance of FGF23 in CKD.

Alfacalcidol vs Calcitriol in the Management of Patient With Hypoparathyroidism: A Randomized Controlled Trial

CONTEXT

Alfacalcidol and calcitriol are commonly used for managing hypoparathyroidism. Their relative merits have not been systematically assessed.

OBJECTIVE

We compared the effect of alfacalcidol and calcitriol on phosphatemic control, hypercalciuria, and associated factors in idiopathic-hypoparathyroidism (IH).

DESIGN AND SETTING

Open-label randomized controlled trial, tertiary care center.

SUBJECTS AND METHODS

IH patients with optimal calcemic control on alfacalcidol were continued on the same (n = 20) or switched to calcitriol (n = 25) at half of the ongoing alfacalcidol dose. The dose was adjusted during follow-up to maintain serum total calcium between 8.0 and 9.5 mg/dL. Serum calcium, phosphorus, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, 24-h urine calcium-to-creatinine ratio, and fractional excretion of phosphorus (FEPh) were measured at baseline and 6 months. Plasma intact-FGF23 was measured at final follow-up.

RESULT

Patients receiving alfacalcidol and calcitriol had comparable serum calcium at 6 months (8.7 ± 0.4 vs 8.9 ± 0.4 mg/dL, P = 0.13). Their median [interquartile range (IQR)] dose at 6 months was 2.0 (1.0-2.5) and 0.75 (0.5-1.0) µg/d, respectively. Serum 1,25(OH)2D levels were physiological in both (35.3 ± 11.6 and 32.3 ± 16.9 pg/mL). Serum phosphate and calcium excretion were comparable in 2 arms. A majority had hyperphosphatemia (75% vs 76%), hypercalciuria (75% vs 72%), and elevated FGF23 (116 ± 68 and 113 ± 57 pg/mL). Age showed significant independent association with plasma FGF23 (β = 1.9, P = 0.001). Average FEPh was low despite high FGF23.

CONCLUSION

At optimal calcium control, both alfacalcidol and calcitriol lead to comparable but high serum phosphate levels, hypercalciuria, physiological circulating 1,25(OH)2D, and elevated FGF23. Further studies are required to systematically investigate other treatment options.

FGF23, a novel muscle biomarker detected in the early stages of ALS

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive muscle weakness. Skeletal muscle is a prime source for biomarker discovery since it is one of the earliest sites to manifest disease pathology. From a prior RNA sequencing project, we identified FGF23 as a potential muscle biomarker in ALS. Here, we validate this finding with a large collection of ALS muscle samples and found a 13-fold increase over normal controls. FGF23 was also increased in the SOD1G93A mouse, beginning at a very early stage and well before the onset of clinical symptoms. FGF23 levels progressively increased through end-stage in the mouse. Immunohistochemistry of ALS muscle showed prominent FGF23 immunoreactivity in the endomysial connective tissue and along the muscle membrane and was significantly higher around grouped atrophic fibers compared to non-atrophic fibers. ELISA of plasma samples from the SOD1G93A mouse showed an increase in FGF23 at end-stage whereas no increase was detected in a large cohort of ALS patients. In conclusion, FGF23 is a novel muscle biomarker in ALS and joins a molecular signature that emerges in very early preclinical stages. The early appearance of FGF23 and its progressive increase with disease progression offers a new direction for exploring the molecular basis and response to the underlying pathology of ALS.

Mistranslation Drives Alterations in Protein Levels and the Effects of a Synonymous Variant at the Fibroblast Growth Factor 21 Locus

Fibroblast growth factor 21 (FGF21) is a liver-derived hormone with pleiotropic beneficial effects on metabolism. Paradoxically, FGF21 levels are elevated in metabolic diseases. Interventions that restore metabolic homeostasis reduce FGF21. Whether abnormalities in FGF21 secretion or resistance in peripheral tissues is the initiating factor in altering FGF21 levels and function in humans is unknown. A genetic approach is used to help resolve this paradox. The authors demonstrate that the primary event in dysmetabolic phenotypes is the elevation of FGF21 secretion. The latter is regulated by translational reprogramming in a genotype- and context-dependent manner. To relate the findings to tissues outcomes, the minor (A) allele of rs838133 is shown to be associated with increased hepatic inflammation in patients with metabolic associated fatty liver disease. The results here highlight a dominant role for translation of the FGF21 protein to explain variations in blood levels that is at least partially inherited. These results provide a framework for translational reprogramming of FGF21 to treat metabolic diseases.

FGF21 serum levels are related to insulin resistance, metabolic changes and obesity in Mexican people living with HIV (PLWH)

Background

Antiretroviral therapy has significantly improved prognosis in treatment against HIV infection, however, prolonged exposure is associated to cardiovascular diseases, lipodystrophy, type 2 diabetes, insulin resistance, metabolic alteration, as obesity which includes the accumulation of oxidative stress in adipose tissue. FGF21 is a peptide hormone that is known to regulate glucose and lipid metabolism. FGF21 is expressed and secreted primarily in the liver and adipose tissue, promoting oxidation of glucose/fatty acids and insulin sensitivity. Alterations in FGF21 may be associated with the development of insulin resistance, metabolic syndrome and cardiovascular disease. We hypothesized that FGF21 protein levels are associated with metabolic abnormalities, placing special attention to the alterations in relation to the concurrence of overweight/obesity in people living with HIV (PLWH).

Design

Serum FGF21 was analyzed in 241 subjects, 160 PLWH and 81 unrelated HIV-uninfected subjects as a control group. Clinical records were consulted to obtain CD4+ cell counting and number of viral RNA copies. Serum FGF21 levels were tested for correlation with anthropometric and metabolic parameters; glucose, cholesterol, HDL, LDL, VLDL, triglycerides, insulin and indexes of atherogenesis and insulin resistance (HOMA).

Results

The participants were classified into four groups: (i) PLWH with normal weight, (ii) PLWH with overweight/obesity, (iii) HIV-uninfected with normal weight, and (iv) HIV-uninfected with overweight/obesity.

Insulin levels were higher in normal-weight PLWH than in the HIV-uninfected group but not statistically significant, however, for the overweight/obesity PLWH group, insulin levels were significantly higher in comparison with the other three groups (p<0.0001). For FGF21, serum levels were slightly higher in the overweight/obesity groups in both patients and controls.

In HIV-infected subjects, FGF21 levels showed a strong positive correlation with triglycerides, insulin levels and insulin resistance with a p-value <0.0001. In the seronegative group, FGF21 was only correlated with weight and waist circumference, showing an important association of FGF21 levels with the degree of obesity of the individuals.

Conclusion

Insulin resistance and FGF21 elevations were observed in overweight-obese PLWH. FGF21 elevation could be viewed as a compensation mechanism as, in the control group, FGF21 correlations appeared to be confined to weight and waist circumference. This can be explained based on the action of FGF21 promoting the uptake of glucose in adipose tissue. In PLWH, FGF21 was low, possibly as a result of a change in adiposity leading to a metabolic disruption.

The bone is the major source of high circulating intact fibroblast growth factor-23 in acute murine polymicrobial sepsis induced by cecum ligation puncture

Fibroblast growth factor-23 (FGF23), a bone-produced hormone, plays a critical role in mineral homeostasis. Human diseases associated with excessive intact circulating FGF23 (iFGF23) result in hypophosphatemia and low vitamin D hormone in patients with normal kidney function. In addition, there is accumulating evidence linking FGF23 with inflammation. Based on these studies and the frequent observation of hypophosphatemia among septic patients, we sought to elucidate further the relationship between FGF23 and mineral homeostasis in a clinically relevant murine polymicrobial sepsis model. Medium-severity sepsis was induced by cecum ligation puncture (CLP) in adult CD-1 mice of both sexes. Healthy CD-1 mice (without CLP) were used as controls. Forty-eight hours post-CLP, spontaneous urine was collected, and serum, organs and bones were sampled at necropsy. Serum iFGF23 increased ~20-fold in CLP compared to control mice. FGF23 protein concentration was increased in the bones, but not in spleen or liver of CLP mice. Despite the ~20-fold iFGF23 increase, we did not observe any significant changes in mineral homeostasis or parathyroid hormone levels in the blood of CLP animals. Urinary excretion of phosphate, calcium, and sodium remained unchanged in male CLP mice, whereas female CLP mice exhibited lower urinary calcium excretion, relative to healthy controls. In line with renal FGF23 resistance, expression of phosphate-, calcium- and sodium-transporting proteins did not show consistent changes in the kidneys of male and female CLP mice. Renal expression of the co-receptor αKlotho was downregulated in female, but not in male CLP mice. In conclusion, our data demonstrate that the dramatic, sex-independent rise in serum iFGF23 post-CLP was mainly caused by an upregulation of FGF23 secretion in the bone. Surprisingly, the upsurge in circulating iFGF23 did not alter humoral mineral homeostasis in the acutely septic mice. Hence, the biological function of elevated FGF23 in sepsis remains unclear and warrants further studies.

Spinal Cord Injury Reduces Serum Levels of Fibroblast Growth Factor-21 and Impairs Its Signaling Pathways in Liver and Adipose Tissue in Mice

Spinal cord injury (SCI) results in dysregulation of carbohydrate and lipid metabolism; the underlying cellular and physiological mechanisms remain unclear. Fibroblast growth factor 21 (FGF21) is a circulating protein primarily secreted by the liver that lowers blood glucose levels, corrects abnormal lipid profiles, and mitigates non-alcoholic fatty liver disease. FGF21 acts via activating FGF receptor 1 and ß-klotho in adipose tissue and stimulating release of adiponectin from adipose tissue which in turn signals in the liver and skeletal muscle. We examined FGF21/adiponectin signaling after spinal cord transection in mice fed a high fat diet (HFD) or a standard mouse chow. Tissues were collected at 84 days after spinal cord transection or a sham SCI surgery. SCI reduced serum FGF21 levels and hepatic FGF21 expression, as well as β-klotho and FGF receptor-1 (FGFR1) mRNA expression in adipose tissue. SCI also reduced serum levels and adipose tissue mRNA expression of adiponectin and leptin, two major adipokines. In addition, SCI suppressed hepatic type 2 adiponectin receptor (AdipoR2) mRNA expression and PPARα activation in the liver. Post-SCI mice fed a HFD had further suppression of serum FGF21 levels and hepatic FGF21 expression. Elevated serum free fatty acid (FFA) levels after HFD feeding were observed in post-SCI mice but not in sham-mice, suggesting defective FFA uptake after SCI. Moreover, after SCI several genes that are implicated in insulin's action had reduced expression in tissues of interest. These findings suggest that downregulated FGF21/adiponectin signaling and impaired responsiveness of adipose tissues to FGF21 may, at least in part, contribute to the overall picture of metabolic dysfunction after SCI.

Effects of increased physical activity and/or weight loss diet on serum myokine and adipokine levels in overweight adults with impaired glucose metabolism

AIM

The purpose of this study was to investigate the changes in serum irisin, fibroblast growth factor-21 (FGF21), visfatin, follistatin like protein-1 (FSTL1), and meteorin-like protein (Metrnl) levels in response to increased physical activity and/or diet interventions in overweight subjects with impaired glucose metabolism (IGM).

METHODS

A total of 60 subjects (BMI > 25.0 kg/m²) with IGM were recruited in this single-centered interventional study. Twelve subjects dropped out during the study and the study was completed with 48 patients. Patients were divided into two groups as diet only (DI, n = 24) and diet and physical activity intervention (DPA, n = 24). Patients in DI group received a diet program while DPA group received a diet combined with a physical activity intervention for 12 weeks. Additional 24 healthy subjects were recruited to compare the baseline levels of proteins. Serum protein levels, anthropometric measurements, and biochemical parameters were assessed.

RESULTS

Irisin, FGF21, visfatin, and FSTL1 levels significantly decreased in both groups after 12-week intervention (p < 0.001). However, there were no differences in protein levels between DI and DPA groups (p > 0.05). Likewise, the total change in weight was similar in both DI (-4.35 kg) and DPA (-4.85 kg) groups (p > 0.05). A 5% reduction in initial body weight with DPA therapy resulted in a stronger correlation between the changes in irisin, visfatin, and FSTL1 levels and fasting glucose and HbA1c levels.

CONCLUSIONS

These results demonstrate that serum irisin, FGF21, visfatin, and FSTL1 levels decreased in response to weight loss interventions. Weight loss induced by DI or DPA therapies had similar lowering effects on these proteins in subjects with IGM, and these myokines might be related to glucose metabolism biomarkers.

High baseline FGF21 levels are associated with poor glucose-lowering efficacy of exenatide in patients with type 2 diabetes

AIMS

To investigate the association between fibroblast growth factor 21 (FGF21) levels and glycemic response to exenatide in patients with type 2 diabetes.

METHODS

The exploratory analysis of a multi-center trial included 190 patients with type 2 diabetes inadequately controlled by monotherapy or combination therapy of metformin and insulin secretagogues. All participants received exenatide twice daily as an add-on therapy for 16 weeks. Serum FGF21 and other information at the baseline and end of follow-ups were obtained. Linear regression analysis was used to determine the correlations between baseline FGF21 levels and HbA1c reduction from baseline after the treatment.

RESULTS

After 16 weeks of treatment with exenatide, a decline in the HbA1c levels from baseline was associated with higher baseline FGF21 levels among all participants (r = 0.193, P = 0.008) and in subgroup of the participants receiving background metformin monotherapy (r = 0.231, P = 0.034). Compared with patients in the lowest FGF21 quartile, patients in the highest FGF21 quartile showed a significantly weakened decline in HbA1c levels from baseline among all participants (β = - 0.16 [95% Cl - 0.31 to - 0.01], P < 0.05) and in subgroup of the participants receiving background metformin monotherapy (β = - 0.23 [95% Cl - 0.43 to - 0.03], P < 0.05), after adjusting for the confounding factors, including age, sex, and baseline HbA1c levels.

CONCLUSIONS

The high baseline FGF21 levels are associated with poor glycemic responses to exenatide in patients with type 2 diabetes. Therefore, FGF21 could be used as a biomarker for predicting the efficacy of exenatide treatment.

TRIAL REGISTRATION

ChiCTR-IPR-15006558, date registered May 27, 2015.

Incidence rate of vitamin D deficiency and FGF23 levels in 12- to 13-year-old adolescents in Japan

INTRODUCTION

The incidence rate of vitamin D deficiency is increasing throughout the world. We measured the incidence rate of vitamin D deficiency and fibroblast growth factor 23 (FGF23) levels in 12- to 13-year-old adolescents in Japan.

MATERIALS AND METHODS

A total of 492 adolescents (247 boys and 245 girls) from Japanese community enrolled in this study. 25 hydroxyvitamin D (25(OH)D) was measured with radioimmunoassay. In the subjects with low 25(OH)D levels (≦ 20 ng/ml), intact parathyroid hormone (iPTH), calcium (Ca), phosphorus (P), albumin (Alb), alkaline phosphatase (ALP) and FGF23 were measured.

RESULTS

25(OH)D levels were significantly lower in girls (20.9 ± 3.1 ng/ml) than in boys (22.2 ± 3.3 ng/ml) (p < 0.0001). Fifty-five boys (22.3%) and 83 (33.9%) girls showed vitamin D deficiency (< 20 ng/ml). One-hundred eighty-six (75.3%) boys and 162 (66.1%) girls showed vitamin D insufficiency (≧ 20 ng/ml, < 30 ng/ml). In the subjects whose 25(OH)D levels were ≦ 20 ng/ml, the levels of iPTH, Ca, P, Alb, ALP and FGF23 were 22.3 ± 9.0 pg/ml, 9.5 ± 0.4 mg/dl, 4.7 ± 0.6 mg/dl, 4.6 ± 0.3 g/dl, 920.8 ± 339.3 U/l and 42.6 ± 26.0 pg/ml, respectively. There was a significant negative association between serum 25(OH)D levels and iPTH [r =  - 0.290 (p < 0.0001)]. There was no significant association between serum 25(OH)D levels and FGF23.

CONCLUSION

We show that 28% of Japanese 12- to 13-year-old early adolescents suffer from vitamin D deficiency. Findings from this study indicate that vitamin D deficiency requires close oversight in public health during adolescence to ensure proper bone health.

The Effect of a Life-Style Intervention Program of Diet and Exercise on Irisin and FGF-21 Concentrations in Children and Adolescents with Overweight and Obesity

Overweight and obesity in childhood and adolescence represent major public health problems of our century, and account for increased morbidity and mortality in adult life. Irisin and Fibroblast Growth Factor 21 (FGF-21) have been proposed as prognostic and/or diagnostic biomarkers in subjects with obesity and metabolic syndrome, because they increase earlier than other traditional biomarkers. We determined the concentrations of Irisin and FGF-21 in children and adolescents with overweight and obesity before and after one year of a life-style intervention program of diet and physical exercise and explored the impact of body mass index (BMI) reduction on the concentrations of Irisin, FGF-21 and other cardiometabolic risk factors. Three hundred and ten (n = 310) children and adolescents (mean age ± SD: 10.5 ± 2.9 years) were studied prospectively. Following one year of the life-style intervention program, there was a significant decrease in BMI (p = 0.001), waist-to-hip ratio (p = 0.024), waist-to-height ratio (p = 0.024), and Irisin concentrations (p = 0.001), and an improvement in cardiometabolic risk factors. There was no alteration in FGF-21 concentrations. These findings indicate that Irisin concentrations decreased significantly as a result of BMI reduction in children and adolescents with overweight and obesity. Further studies are required to investigate the potential role of Irisin as a biomarker for monitoring the response to lifestyle interventions and for predicting the development of cardiometabolic risk factors.

Constitutive depletion of Slc34a2/NaPi-IIb in rats causes perinatal mortality

Absorption of dietary phosphate (Pi) across intestinal epithelia is a regulated process mediated by transcellular and paracellular pathways. Although hyperphosphatemia is a risk factor for the development of cardiovascular disease, the amount of ingested Pi in a typical Western diet is above physiological needs. While blocking intestinal absorption has been suggested as a therapeutic approach to prevent hyperphosphatemia, a complete picture regarding the identity and regulation of the mechanism(s) responsible for intestinal absorption of Pi is missing. The Na+/Pi cotransporter NaPi-IIb is a secondary active transporter encoded by the Slc34a2 gene. This transporter has a wide tissue distribution and within the intestinal tract is located at the apical membrane of epithelial cells. Based on mouse models deficient in NaPi-IIb, this cotransporter is assumed to mediate the bulk of active intestinal absorption of Pi. However, whether or not this is also applicable to humans is unknown, since human patients with inactivating mutations in SLC34A2 have not been reported to suffer from Pi depletion. Thus, mice may not be the most appropriate experimental model for the translation of intestinal Pi handling to humans. Here, we describe the generation of a rat model with Crispr/Cas-driven constitutive depletion of Slc34a2. Slc34a2 heterozygous rats were indistinguishable from wild type animals under standard dietary conditions as well as upon 3 days feeding on low Pi. However, unlike in humans, homozygosity resulted in perinatal lethality.

Western Diet Aggravated Carbon Tetrachloride-Induced Chronic Liver Injury by Disturbing Gut Microbiota and Bile Acid Metabolism

SCOPE

The high-fat, high-sucrose, and low-fiber Western diet (WD) is popular in many countries and affects the onset and progression of many diseases. This study is aimed to explore the influence of the WD on chronic liver disease (CLD) and its possible mechanism.

METHODS AND RESULTS

C57BL/6 mice are given a control diet (CD) or WD and CLD is induced by intraperitoneally injecting carbon tetrachloride (CCL4 ) twice a week for 8 weeks. The WD aggravated CCL4 -induced chronic liver injury, as evidenced by increased serum transaminase levels, worsened hepatic inflammatory response, and fibrosis. Gut microbiota is disturbed in mice treated with CCL4 +WD (WC group), manifested as the accumulation of Fusobacteria, Streptococcaceae, Streptococcus, Fusobacterium, and Prevotella and the depletion of Firmicutes, Lachnospiraceae, and Roseburia. Additionally, increased hepatic taurocholic acid in the WC group activated sphingosine-1-phosphate receptor 2, which is positively correlated with hepatic fibrosis and inflammation parameters. Mice in the WC group have higher fecal primary bile acid (BA) levels and lower fecal secondary/primary BA ratios. Serum FGF15 levels are also elevated in the WC group, which is positively correlated with hepatic inflammation.

CONCLUSION

WD accelerates the progression of CLD which is associated with changes in the gut microbiota and BA metabolism.

Circulating levels of fibroblast growth factor 21 in gestational diabetes mellitus: a meta-analysis

In recent times, the role of fibroblast growth factor 21 (FGF21) in patients with gestational diabetes mellitus (GDM) has been increasingly investigated. However, to our knowledge, no systematic analysis has been conducted yet to evaluate the relationship between FGF21 levels and GDM. Confirmed studies related to circulating FGF21 levels and GDM were searched from the databases of PubMed, ISI Web of Science, MEDLINE and EMBASE. Data were reported as standard mean difference (SMD) and associated 95% confidence intervals (CIs). Analysis were performed with Review Manager 5.2 and Stata version 11.0. A total of 392 cases and 435 controls in nine articles were included in this meta-analysis. The circulating FGF21 levels in pregnant women with GDM was higher than that in controls (random effects MD [95% CI] = 0.46, [0.07-0.86], p = 0.02). The result of multivariate meta-regression showed that sample size and point of sample collection contributed to heterogeneity (p = 0.033 and p = 0.047, respectively). Additionally, the results showed that there was no publication bias in this meta-analysis (Z = 1.36, p = 0.175; t = 1.24, p = 0.256, respectively). To conclude, this meta-analysis provides evidence that circulating FGF21 levels are higher in GDM subjects than controls, and it is important to clarify the relationship between circulating FGF21 levels and pregnant women with GDM in accurate prediction of GDM.

The potential role of plasma fibroblast growth factor 21 as a diagnostic biomarker for abdominal aortic aneurysm presence and development

AIMS

Fibroblast growth factor 21 (FGF21) has been identified as the master hormonal regulator of energy balance, its elevation is observed in a series of metabolic and cardiovascular diseases. Studies have implicated the role of FGF21 signaling in the pathogenesis of abdominal aortic aneurysm (AAA). We will investigate the association of FGF21 and AAA development.

MATERIALS AND METHODS

In this study, we assayed plasma levels of FGF21 in 82 patients with AAA and 44 control subjects, then analyzed their relationship with clinical, biochemical and histological phenotypes. The expression of β-klotho, an essential co-receptor of FGF21, was assessed with IHC staining and RT-qPCR. Machine learning models incorporate a combination of FGF21 and clinical data were utilized in the prediction of AAA occurrence.

KEY FINDINGS

FGF21 was statistically higher in patients with AAA (781 pg/ml [533, 1213]) than in control subjects (567 pg/ml [324, 939]). After adjustment for age and BMI, we found a positive association of FGF21 levels with AAA diameters, hypertension rate and hsCRP, and a negative correlation between FGF21 levels and HDL-c. Furthermore, the protein levels of β-klotho in abdominal aorta of AAA were found significantly lower than in control group indicating the presence of FGF21 resistance. Combining FGF21 levels with four clinical characteristics significantly improved the stratification of AAA and control groups with an AUC of 0.778.

SIGNIFICANCE

Combining detection of plasma FGF21 and clinical characteristics may be reliable for identifying the presence of AAA. The role of FGF21 as a therapeutic target of AAA warrants further investigation.

Do the Heterozygous Carriers of a CYP24A1 Mutation Display a Different Biochemical Phenotype Than Wild Types?

CONTEXT

Human cytochrome P450 24 subfamily A member 1 (CYP24A1) loss-of-function mutations result in impaired activity of the 24-hydroxylase involved in vitamin D catabolism, thus inducing a vitamin D-dependent hypercalcemia. Homozygotes often present an overt clinical phenotype named idiopathic infantile hypercalcemia (IIH), whereas it is debated whether heterozygotes display an abnormal phenotype.

OBJECTIVE

To compare the clinical and biochemical features of heterozygous carriers of CYP24A1 variant and healthy wild-type controls sharing the same genetic and environmental exposure.

METHODS

A large family harboring the nonsense c.667A>T, p.Arg223* pathogenic variant in the CYP24A1 gene was evaluated. All subjects underwent clinical and biochemical evaluation and complete analysis of vitamin D metabolites using mass spectroscopy including 1,24,25(OH)3D3. Subjects were divided into 2 groups according to their genotype: heterozygotes and wild-type for the CYP24A1 variant.

RESULTS

The proband, a 40-year-old man, homozygous for p.Arg223* pathogenic variant, had a history of mild hypercalcemia with a seasonal trend, recurrent nephrolithiasis, and no episodes of acute hypercalcemia. He showed the highest serum levels of fibroblast growth factor 23, the highest 25(OH)D3/24,25(OH)2D3 ratio and undetectable levels of 1,24,25(OH)3D3, which represent indicators of a loss-of-function CYP24A1. Compared with the wild-types, heterozygotes had higher serum calcium and 25(OH)D3 concentrations (P = .017 and P = .025, respectively), without any difference in the other biochemical parameters and in the rate of nephrolithiasis.

CONCLUSION

Heterozygotes exhibit a biochemical phenotype different from that of wild-type subjects. In clinical practice, these individuals might require surveillance because of the potential risk of developing hypercalcemia and related clinical manifestations if exposed to triggering factors.

Baseline serum angiopoietin-2 and VEGF levels predict the deterioration of the liver functional reserve during lenvatinib treatment for hepatocellular carcinoma

A deteriorated liver functional reserve during systemic therapy for unresectable hepatocellular carcinoma (HCC) causes poor patient outcomes. We aimed to identify predictive factors associated with the deterioration of Child-Pugh score at 8 weeks after lenvatinib initiation. Patients with adequate clinical data and baseline preserved serum samples available were included. Baseline fibroblast growth factor (FGF)19 and 21, angiopoietin (ANG)2, and vascular endothelial growth factor (VEGF) levels were evaluated. Thirty-seven patients were included, and 6, 15, 14, and 2 experienced complete response, partial response, stable disease, and progressive disease, respectively. Twenty-four (65%) and 13 (35%) patients showed a maintained/improved and deteriorated Child-Pugh-score, respectively. While baseline clinical data, treatment response, and laboratory data were similar between these two patient groups, baseline ANG2 and VEGF levels were significantly higher (P = 0.0017) and lower (P = 0.0231), respectively, in patients with deteriorated Child-Pugh score than in those without. Based on receiver operating characteristic curve analysis, cut-off values for ANG2 and VEGF were found to be 3,108 pg/mL and 514.9 pg/mL, respectively. Among patients with low VEGF and high ANG2, 89% (8/9) exhibited a deteriorated Child-Pugh score, whereas none of the patients (0/9) with high VEGF and low ANG2 did. The deterioration of the Child-Pugh score in patients with unresectable HCC who are treated with lenvatinib may be predictable based on combined baseline serum ANG2 and VEGF levels.

Association between serum fibroblast growth factor 21 level and sight-threatening diabetic retinopathy in Chinese patients with type 2 diabetes

INTRODUCTION

We conducted this cross-sectional study to explore the relationship between serum fibroblast growth factor 21 (FGF21) level and sight-threatening diabetic retinopathy (STDR).

RESEARCH DESIGN AND METHODS

A total of 654 patients with type 2 diabetes were recruited. Diabetic retinopathy (DR) was evaluated by the bilateral retinal photography, and patients were assigned into groups of no DR (NDR) (n=345, 52.75%), non-sight-threatening diabetic retinopathy (NSTDR) (n=207, 31.65%), involving patients with mild or moderate non-proliferative retinopathy (NPDR) and STDR (n=102, 15.60%), including those with severe NPDR or proliferative diabetic retinopathy (PDR). Serum FGF21 levels were quantified by a sandwich ELISA. Patients were divided into quartiles according to their serum FGF21 level.

RESULTS

There was a significant difference in serum FGF21 level among the three groups of patients (p<0.01). Compared with other quartiles (Q1-Q3), the patients in Q4 had a higher prevalence of DR and STDR (p<0.05). Compared with Q1, a positive association was observed between serum FGF21 level and DR in Q3 and Q4 (p<0.01). After adjusting for age, gender and other risk factors, serum FGF21 level in Q4 was found to be associated with increased risk of DR and STDR (p<0.01). Serum FGF21 level was noted as an independent risk factor for DR and STDR (p<0.01). Serum FGF21 level >478.76 pg/mL suggested the occurrence of DR and that level >554.69 pg/mL indicated STDR (p<0.01).

CONCLUSIONS

Serum FGF21 level was a biomarker for the risk of developing DR or STDR. The risk of STDR increased when the serum FGF21 level of patients with type 2 diabetes was >554.69 pg/mL.

Epigenetic Regulation of Processes Related to High Level of Fibroblast Growth Factor 21 in Obese Subjects

We hypothesised that epigenetics may play an important role in mediating fibroblast growth factor 21 (FGF21) resistance in obesity. We aimed to evaluate DNA methylation changes and miRNA pattern in obese subjects associated with high serum FGF21 levels. The study included 136 participants with BMI 27-45 kg/m2. Fasting FGF21, glucose, insulin, GIP, lipids, adipokines, miokines and cytokines were measured and compared in high serum FGF21 (n = 68) group to low FGF21 (n = 68) group. Human DNA Methylation Microarrays were analysed in leukocytes from each group (n = 16). Expression of miRNAs was evaluated using quantitative PCR-TLDA. The study identified differentially methylated genes in pathways related to glucose transport, insulin secretion and signalling, lipid transport and cellular metabolism, response to nutrient levels, thermogenesis, browning of adipose tissue and bone mineralisation. Additionally, it detected transcription factor genes regulating FGF21 and fibroblast growth factor receptor and vascular endothelial growth factor receptor pathways regulation. Increased expression of hsa-miR-875-5p and decreased expression of hsa-miR-133a-3p, hsa-miR-185-5p and hsa-miR-200c-3p were found in the group with high serum FGF21. These changes were associated with high FGF21, VEGF and low adiponectin serum levels. Our results point to a significant role of the epigenetic regulation of genes involved in metabolic pathways related to FGF21 action.